Publication details

Ordering Constraints over Feature Trees

Martin Müller, Joachim Niehren, Andreas Podelski

Constraints, an International Journal 5(1--2):7-42, January 2000

Feature trees are the formal basis for algorithms manipulating record like structures in constraint programming,
computational linguistics and in concrete applications like software
configuration management. Feature trees model records, and
constraints over feature trees yield extensible and modular record
descriptions. We introduce the constraint system
FT$_leq$ of
ordering constraints interpreted over feature trees. Under the view
that
feature trees represent symbolic information, the relation
$leq$
corresponds to the information ordering (``carries less information
than''). We present two algorithms in cubic time, one for the
satisfiability problem and one for the entailment problem of
FT$_leq$.
We show that
FT$_leq$
has the independence property. We are thus able
to handle negative conjuncts via entailment and obtain a cubic
algorithm that decides the satisfiability of conjunctions of
positive and negated ordering constraints over feature trees.
Furthermore, we reduce the satisfiability problem of Dörre's weak
subsumption constraints to the satisfiability problem of
FT$_leq$ and
improve the complexity bound for solving weak subsumption
constraints from $O(n^5)$ to $O(n^3)$.